The Impact has a breech plug just like the Omega and non-speed breech Encore, so it should not be a problem at all. I've shot 20+ shots with BH209 without cleaning or swabbing my Omega.
CVA now offers an optional breech plug SPECIFICALLY for shooting BH209. It's only about $20. If you have an Optima, I would get the new breach plug before I try any other mods.